An adjustable speed drive (“ASD”) controls the power supplied from a source, such as a utility or generator, and a motor. However, the ASD, as well as power electronics in general, suffer when the power supplied to the ASD is of poor quality. Poor power quality is sometimes represented as transients or harmonics in the power signal, such as overvoltages, voltage sags, and brief interruptions. One cause of transients is the addition of capactive devices, such as other ASDs or capacitor banks, on the power supply side of the ASD. Poor power quality can result in device, such as power semiconductor device, failures in the ASD. This in turn results in undesirable down time for the motor and the application of the motor. In medium voltage applications, a motor being down results in lost productivity for a manufacturing plant. Power quality considerations are described in Power Quality Considerations for Adjustable Speed Drive Applications, published by the Electric Power Institute, which is hereby incorporated by reference. Accordingly, there is a need to protect ASDs from damage due to transients in the power supplied from the source.